This invention relates to defibrillators for cardiac resuscitation and, in particular, to carrying cases for defibrillators.
Cardiac arrest is a life-threatening medical condition in which the patient's heart fails to provide blood flow to support life. A defibrillator can be used to deliver defibrillating shocks to a patient suffering from cardiac arrest. The defibrillator resolves this condition by delivering a high-voltage impulse to the heart in order to restore normal rhythm and contractile function in patients who are experiencing arrhythmia such as VF (ventricular fibrillation) or VT (ventricular tachycardia) that is not accompanied by spontaneous circulation. One type of defibrillator, the automated external defibrillator (AED), differs from manual defibrillators in that the AED can automatically analyze the electrocardiogram (ECG) rhythm to determine if defibrillation is necessary. The defibrillator analyzes the ECG signal for signs of arrhythmia. If VF is detected, the defibrillator signals the rescuer that a shock is advised. After the detection of VF or other shockable rhythm, the rescuer presses a shock button on the defibrillator to deliver a defibrillation pulse to resuscitate the patient.
Defibrillation must be delivered very soon after the onset of cardiac arrest in order to be effective. It is estimated that the chance of survival falls by 10% for every minute of delay to defibrillation beyond four minutes after cardiac arrest. Hence, AEDs are designed to be used by first responders, such as firefighters, police, or lay bystanders, who are the most likely to arrive at the patient's side first. Once an AED is brought to the patient, the rescuer must deploy and use it quickly. Such quick use is often challenging, because the rescuer may be unfamiliar with the AED's setup and operation.
External defibrillators act through electrode pads applied across the chest of the patient. The electrodes adhesively attach to the patient and are used both to acquire an ECG signal from the patient's heart and to apply the defibrillating shock. AED electrodes commonly are formed by locating a foil or metalized electrode between a flexible nonconductive backing and a conductive adhesive gel. The conductive adhesive attaches the electrode securely to the patient. Gels, however, will dry out (desiccate) over time and have a finite shelf life. A typical shelf life for an electrode with gel adhesive is about two years, after which the electrodes must be replaced. Some AEDs use electrodes which are simply replaced when the safe shelf life period has expired. Other AEDs have an internal self-test circuit which periodically tests the electrodes and detects desiccation by an impedance change. For self-test electrodes the electrodes are electrically connected to each other to form a continuous closed loop circuit that is tested. The closed loop circuit is broken when the electrode pads are deployed for use.
In the case of both self-tested electrodes and non-self-tested electrodes, it is typical that the electrodes will be connected to the AED while stored prior to use so that the rescuer does not need to connect them during the emergency; they are already pre-connected and ready for use. Pre-connected electrodes are commonly stored inside a protective container that is the same or co-located as a carrying case for an AED, so that the electrodes are protected from puncture or damage during storage, yet are instantly available for deployment when the AED case is opened.
Some AEDs also include accessories which aid in the administration of cardiopulmonary resuscitation (CPR) during the rescue. For example, the QCPR meter, sold by Philips Electronics North America, is a puck-like sensor which is placed on the patient's chest, and over which manual CPR compressions are applied. The QCPR meter contains force and motion sensors which provide an indication of the quality of the CPR applied via a signal cable to a defibrillator.
The AED may also include a pediatric mode accessory that, when applied to the AED, causes the AED to analyze and provide therapy appropriate to pediatric patients. The pediatric mode accessory may be shaped like a key which is inserted into an AED socket for use. When not in use, the key is stored elsewhere in the carrying case.
In addition, AED carrying cases may also include a fast response kit, which contains such rescue items as sterile gloves, scissors for cutting clothing away from a patient's chest, a razor for shaving excess chest hair, and a rescue breathing shield. A spare battery for the AED, spare electrode set, and written user guide may also be included in the carrying case.
Prior art AED carrying cases suffer a number of problems. First, the cover and handle on some prior art carrying cases hamper the application of therapy to the patient. Handles typically consist of strapping, which easily tangles with other gear stored or carried by the rescuer, delaying deployment. Handles may also be arranged to cover the AED cover latch, which may impede the ability of a glove-wearing rescuer to open the cover. Carrying case lids, when open, may be disposed such that they can easily be stepped on and broken by the rescuer, kicked shut by the rescuer, or otherwise impede access to the patient lying alongside. All of these characteristics serve to delay therapy.
Next, some carrying cases are arranged such that important contents are not visible at the time of deployment. A fast response kit, for example, may be stored in a separate pocket from the AED. A rescuer using such a carrying case may be delayed in finding and/or deploying the kit during rescue.
Prior art carrying case latches may be insufficiently robust to prevent inadvertent opening when the case is dropped, thus exposing the contents to damage or otherwise delaying the rescue. Some latches are simply Velcro closures.
Prior art carrying cases may be ill-disposed for ease of cleaning and checking of the contents, presenting risk of cross-contamination and malfunction during the next rescue. For example, some prior art AED carrying cases have no internal trays that are removable for cleaning. None have any means of testing internal components, such as a CPR guidance device or the defibrillator push buttons, prior to the rescue. If the AED contained in the carrying case has a ready-for-use indicator on its face, the case window may be too small to allow easy viewing of the indicator.